Simplify GetIntrinsicDefault impl
Simplify GetIntrinsicDefault impl

Reviewed By: thedavekwon

Differential Revision: D38967875

fbshipit-source-id: fed19b5084b0debbf49bcf0745061d1340e85e7f

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift